LDL Cholesterol Calculator: Friedewald Formula, Normal Range & Interpretation
Learn how LDL cholesterol is calculated using the Friedewald equation. Understand the LDL-C formula, cholesterol units, VLDL estimation, calculation example, LDL categories, interpretation, and important limitations.
LDL Cholesterol Calculator
Calculate LDL cholesterol using the Friedewald formula from total cholesterol, HDL cholesterol, and triglycerides.
Open LDL Cholesterol Calculator →This article is prepared as a laboratory calculation and education reference. It explains the conventional Friedewald method for estimated LDL-C, including its mathematical basis, unit conversion, calculation steps, and important analytical limitations.
What Is LDL Cholesterol?
Low-density lipoprotein cholesterol (LDL-C) represents the cholesterol carried within low-density lipoprotein particles. LDL-C is an important laboratory measurement used in the assessment and management of cardiovascular risk.
A lipid profile commonly includes total cholesterol (TC), HDL cholesterol (HDL-C), triglycerides (TG), and LDL cholesterol (LDL-C). LDL-C may be measured directly by a laboratory method or estimated using a calculation such as the Friedewald equation.
The Friedewald equation remains a widely recognized method for estimating LDL-C when the required lipid measurements are available and the method's limitations are respected.
Use the LabProSuite LDL Cholesterol Calculator to calculate estimated LDL-C using the Friedewald equation.
What Is the Friedewald Equation?
The Friedewald equation estimates LDL-C from three routinely measured lipid parameters:
- Total cholesterol (TC)
- HDL cholesterol (HDL-C)
- Triglycerides (TG)
The equation estimates VLDL cholesterol from triglycerides using the traditional TG/5 relationship in mg/dL.
Friedewald LDL Cholesterol Formula
Where:
- LDL-C = estimated LDL cholesterol in mg/dL
- TC = total cholesterol in mg/dL
- HDL-C = HDL cholesterol in mg/dL
- TG = triglycerides in mg/dL
Friedewald Formula in mmol/L
When cholesterol and triglycerides are expressed in mmol/L, the traditional Friedewald equation uses TG/2.2 rather than TG/5.
How Is VLDL Estimated in the Friedewald Formula?
The traditional Friedewald equation assumes that triglyceride-rich VLDL cholesterol can be estimated from triglycerides.
Therefore, the equation can also be understood as:
Rearranging this relationship produces the Friedewald LDL-C calculation.
LDL Cholesterol Calculation Example
Consider a hypothetical lipid profile with:
- Total cholesterol: 200 mg/dL
- HDL cholesterol: 50 mg/dL
- Triglycerides: 150 mg/dL
VLDL-C = TG ÷ 5
150 ÷ 5 = 30 mg/dL
LDL-C = TC − HDL-C − VLDL-C
LDL-C = 200 − 50 − 30
This example demonstrates the mathematical calculation only. Clinical interpretation depends on the patient's overall cardiovascular risk and applicable treatment guidelines.
Calculate LDL-C Online
Enter total cholesterol, HDL cholesterol, and triglycerides to calculate LDL cholesterol using the Friedewald equation.
Calculate LDL Cholesterol →LDL Cholesterol Unit Conversion
Laboratories may report cholesterol concentrations in either mg/dL or mmol/L.
| Parameter | mg/dL → mmol/L | mmol/L → mg/dL |
|---|---|---|
| Total Cholesterol | ÷ 38.67 | × 38.67 |
| HDL-C | ÷ 38.67 | × 38.67 |
| LDL-C | ÷ 38.67 | × 38.67 |
| Triglycerides | ÷ 88.57 | × 88.57 |
LDL Cholesterol Levels
LDL-C values are commonly described using categories such as optimal, near optimal, borderline high, high, and very high. However, treatment decisions should not be based on the LDL-C number alone.
| LDL-C | Common Description |
|---|---|
| <100 mg/dL | Optimal |
| 100–129 mg/dL | Near optimal / above optimal |
| 130–159 mg/dL | Borderline high |
| 160–189 mg/dL | High |
| ≥190 mg/dL | Very high |
LDL-C treatment goals are risk-dependent. A single universal LDL target does not apply to every patient. Current cardiovascular guidance uses overall ASCVD risk and clinical context when determining management.
Limitations of the Friedewald Formula
The Friedewald equation is convenient, but it is not a direct measurement of LDL-C and has important limitations.
- Accuracy decreases as triglyceride concentration increases.
- The traditional equation should not be used when triglycerides are ≥400 mg/dL.
- The equation can underestimate LDL-C, particularly when LDL-C is low and triglycerides are elevated.
- The calculation depends on the accuracy of total cholesterol, HDL-C, and triglyceride measurements.
- The traditional TG/5 relationship is an approximation and may not accurately represent VLDL-C in every patient.
When triglycerides are very high, particularly at or above 400 mg/dL, the traditional Friedewald calculation should not be used. Alternative approaches such as an appropriate LDL-C estimation method, direct measurement, or assessment of non-HDL-C may be considered according to the clinical and laboratory context.
LDL-C vs Non-HDL Cholesterol
Non-HDL cholesterol provides another useful measure of atherogenic cholesterol and can be calculated from total cholesterol and HDL-C.
Non-HDL-C includes cholesterol contained in several atherogenic lipoproteins, not only LDL particles. It can therefore provide useful additional information, particularly when triglycerides are elevated.
Friedewald vs Other LDL-C Calculation Methods
The Friedewald equation is not the only method available for estimating LDL-C. Modern laboratory and clinical practice may also use methods such as the Martin-Hopkins equation and the Sampson-NIH equation.
| Method | Main Feature |
|---|---|
| Friedewald | Traditional TG/5 estimation |
| Martin-Hopkins | Uses an adjustable TG/VLDL-C factor |
| Sampson-NIH | Uses a newer mathematical model incorporating triglycerides and non-HDL-C |
| Direct LDL-C | Laboratory assay rather than calculated LDL-C |
The appropriate method depends on the laboratory method, triglyceride concentration, LDL-C level, clinical context, and applicable laboratory or clinical guidance.
When Should Friedewald LDL-C Not Be Used?
The traditional Friedewald equation should not be used when triglycerides are 400 mg/dL or higher. At high triglyceride concentrations, the assumed relationship between triglycerides and VLDL cholesterol becomes unreliable.
The equation may also become less accurate with moderately elevated triglycerides and at very low LDL-C concentrations.
In these situations, the laboratory may use an alternative LDL-C estimation method or another lipid marker according to the laboratory and clinical setting.
How to Use the LabProSuite LDL Calculator
- Enter the total cholesterol value.
- Enter the HDL cholesterol value.
- Enter the triglyceride value.
- Select the appropriate unit.
- Click the calculate button.
- Review the calculated LDL-C result.
- Consider the triglyceride level and the limitations of the Friedewald equation before interpreting the result.
Why Is LDL Cholesterol Important?
LDL-C is an important component of cardiovascular risk assessment. Persistently elevated LDL-C is associated with increased atherosclerotic cardiovascular disease risk.
However, LDL-C should be interpreted together with other factors, including age, blood pressure, diabetes status, smoking, previous cardiovascular disease, family history, triglycerides, HDL-C, non-HDL-C, and other relevant risk markers.
Current 2026 AHA/ACC dyslipidemia guidance emphasizes risk-based management and again incorporates LDL-C and non-HDL-C treatment goals according to cardiovascular risk category.
Frequently Asked Questions About LDL Cholesterol
What is the Friedewald formula for LDL cholesterol?
The traditional Friedewald formula in mg/dL is: LDL-C = Total Cholesterol − HDL-C − (Triglycerides ÷ 5).
How is LDL cholesterol calculated in mmol/L?
When lipid concentrations are expressed in mmol/L, the traditional Friedewald equation is LDL-C = TC − HDL-C − (TG ÷ 2.2).
What triglyceride level makes the Friedewald formula unreliable?
The traditional Friedewald calculation should not be used when triglycerides are 400 mg/dL or higher. Accuracy can also decrease before that threshold, particularly with elevated triglycerides and low LDL-C values.
What is VLDL in the Friedewald equation?
In the traditional Friedewald equation, VLDL cholesterol is estimated as triglycerides divided by 5 when values are expressed in mg/dL.
Is calculated LDL the same as direct LDL?
No. Calculated LDL-C is estimated mathematically from other lipid measurements, while direct LDL-C is obtained using a laboratory assay. Different methods can produce different results.
Is LDL cholesterol of 100 mg/dL normal?
An LDL-C value around 100 mg/dL is commonly described as near optimal or optimal depending on the classification used. The appropriate LDL-C goal depends on overall cardiovascular risk and clinical context.
What does LDL cholesterol above 190 mg/dL mean?
An LDL-C level of 190 mg/dL or higher is considered very high and can be associated with severe hypercholesterolemia. Such a result should be clinically evaluated rather than interpreted using the LDL number alone.
Can the Friedewald formula be used with triglycerides above 400 mg/dL?
No. The traditional Friedewald equation should not be used at triglyceride concentrations of 400 mg/dL or higher because the estimated VLDL relationship becomes unreliable.
What is non-HDL cholesterol?
Non-HDL cholesterol is calculated as total cholesterol minus HDL cholesterol. It represents cholesterol carried by a range of atherogenic lipoproteins.
Which LDL calculation method is most accurate?
No single method is best for every situation. Friedewald is a traditional method, while Martin-Hopkins and Sampson-NIH equations may provide improved estimation in selected situations. The appropriate method depends on triglycerides, LDL-C concentration, laboratory methods, and clinical context.
Conclusion
The Friedewald equation provides a convenient traditional method for estimating LDL cholesterol from total cholesterol, HDL cholesterol, and triglycerides.
For mg/dL values, the equation is LDL-C = TC − HDL-C − TG/5. For mmol/L values, the corresponding traditional equation uses TG/2.2.
The calculation should always be interpreted with awareness of its limitations, particularly when triglycerides are elevated or LDL-C is very low.
For a quick calculation, use the LabProSuite LDL Cholesterol Calculator .
Disclaimer
This article and calculator are provided for educational and laboratory reference purposes only. Calculated LDL-C is an estimate and should not be used as the sole basis for diagnosis or treatment decisions.
Clinical interpretation should be performed by a qualified healthcare professional using the complete lipid profile, cardiovascular risk assessment, applicable guidelines, and clinical context.
References
Lipid measurements in the management of cardiovascular diseases: Practical recommendations
2026 Guideline on the Management of Dyslipidemia
Guidelines for the Management of Dyslipidemia
Clinical Practice Guidelines for Management of Dyslipidemia
Guidelines on Laboratory Diagnostics of Lipid Metabolism Disorders
